Nuttx, LVGL V9, SAMA5D2, display tearing/artefacts

How-to
1

I have a board with a SAMA5D27 processor, running NuttX, with an 800x480 tft.

I can run the lvgl demos, or my own simple screen with just a spinner, but I’m seeing tearing of the video. The spinner, for example, breaks up at times with visible artefacts

My hunch is it’s because the native NuttX interface to the SAMA5D2 is a single framebuffer; lvgl is using lv_nuttx_fbdev.c, with just 1 “plane”, and one buffer, and I think the lvgl writes to the buffer overlap the dma of the framebuffer to the LCD. I can’t readily see how to work around that.

In the past, without an OS in the way, I could use the SAMA5 LCD peripheral very successfully with my “own” pair of framebuffers and it worked just fine.

Is my hunch on the right track? What is the correct way to sort this - but retain NuttX in the mix please?

2

After some more investigation I see the LVGL frame buffer does support 2 buffers, and whether 2 are used is determined by vinfo and pinfo data. So probably more to do with how the SAMA5D2 LCDC is exposed and I may need a custom board-level driver to avoid breaking the existing SAMAD2 support in NuttX.

Still interested in opinions and suggestions.

3

Reverted to V8 and problem has gone, Raised an issue on github as I can’t fix this without input